<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        iframe {
            width: 800px;
            height: 400px;
            border: 1px solid #000;
        }
    </style>
</head>

<body>
    <!-- 通过a标签进行iframe网络地址的切换 -->
    <a href="./login.html" target="fm">点我跳转</a>
    <!-- 就是用来展示别的html页面的 -->
    <iframe src="http://www.taobao.com" frameborder="0" name="fm"></iframe>
</body>

</html>